I am trying to locate a ringing sensation in a 105 year old upright grand piano. The low F and F# generate a ringing or humming - much like you'd hear if you held a tuning fork up to a microphone. I've spent over 3 hours trying to locate the cause to no avail. It is loudest in the bottom section about a foot above the pedals. The dampers appear to be working properly and I've held all the other strings with my hand while playing those notes but the ring continues. Any ideas would be appreciated!

Take a felt strip as a mute and gradually mute off each string and you will eventually find it, hopefully before you have to retire...

I'd like to see that actually; holding all of the strings with one hand.... your hands must be pretty big....

Also check the dummy damper to make sure the spring isn't broken. Could be worn out dampers. Many times, an overtone will ring through elsewhere in certain pianos.

You sure it's not your ears ringing? You're being talked about now in here.

Are you a technician? I assume not, due to the reference about the section "about a foot above the pedals" - what does that mean???
Call in a technician if the sound really bothers you. Be prepared to hear news of extensive re-conditioning on your 105 year old piano.

Could be loose bridge pins, or loose anything on a piano that old, but the bridge is above the pedals. pm me if you want more info.

Could it be that the section that is suppose to be non speaking from Bridge to the hitch pin be noisy? This section is usually muted with felt woven through the strings. Moths and old age may have rotted out this felt cause sympathy noise combined with old dampers.

Could be aliens.

Wow! At 105 years it could be anything! I wouldn't rule out aliens either. The tricky little space devils!

Be sure to check out the damper system thoroughly.

Maybe it's the mice singing along? Or, the kitty purring after eating the little critters.

Could be previous owners' souls in the piano. Only you can free them!